A QuickTime animation of GOES-12 imager 6.5 micrometer (“water vapor channel”) imagery (above) reveals an interesting vortex associated with a cutoff upper-level low which was migrating eastward from Illinois to Ohio on 13 Sepember. Several pulses of convection can be seen developing along the periphery of the vortex. In addition, GOES-12 sounder total column ozone values were slightly elevated within the core of the vortex (~350 Dobson Units, compared to the background of ~300 DU), suggesting that some stratospheric air was also present.

Also of interest were the subtle indications that the structure of the jet stream (within the southeastern quadrant of the upper low circulation) was very complex — note the “streaky” appearance on the water vapor images across the Tennessee and Ohio River Valley regions, especially evident on the 1km resolution MODIS water vapor channel (below, upper right panel), but also apparent on the 10km resolution GOES-12 sounder water vapor channel (below, lower left panel). The relatively smooth NAM 300mb wind speeds simply indicated a broad jet streak core oriented SW-NE from Mississippi to Virginia, with a 500mb jet streak axis located farther to the northwest. The striated appearance of the water vapor imagery suggests that the broad jet core region may have been comprised of multiple jet streaks (likely existing at different altitudes).

The lower right panel below is the CRAS model forecast of the GOES water vapor channel, close to the time of the actual satellite images in the other 3 panels; while the CRAS model was unable to resolve the fine mesoscale structure associated with the multiple jet streak cores, it did offer a good prognosis of the “3-pronged structure” of the leading edge of the dry slot.

After reaching Category 3 intensity over the eastern Atlantic Ocean on 14 October, Hurricane Ophelia (storm track) rapidly underwent transition to an extratropical storm which eventually spread high winds across much of Ireland and the United Kingdom on 16 October 2017. EUMETSAT Meteosat-10 upper-level Water Vapor (6.25 µm) (above) and lower-level Water Vapor (7.35 µm) images (below) revealed the familiar “scorpion tail” signature of a sting jet (reference). Hourly wind gusts (in knots) from primary reporting stations are plotted in red.

Two sites with notable wind gusts were Cork, Ireland (67 knots at 0930 UTC) and Valley, UK (70 knots at 1500 UT), shown below. In fact, a wind gust of 103 knots (119 mph or 191 km/hour) was reported at the Fastnet Rock Lighthouse off the southwest coast of Ireland.

Time series plot of surface data from Cork, Ireland [click to enlarge]

Time series plot of surface data from Valley, United Kingdom [click to enlarge]

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Terra and Aqua MODIS true-color images [click to enlarge]

In a toggle between Terra MODIS (overpass time around 1159 UTC) and Aqua MODIS (overpass time around 1345 UTC) true-color Red-Green-Blue (RGB) imagery (above), a somewhat hazy appearance was seen over the Irish Sea on the Terra MODIS image. This was due to an airborne plume of sand from the Sahara Desert (UK Met Office story).

In fact, blowing sand was observed about 3 hours later at Isle of Man, from 1520-1620 UTC — during that time period their surface winds gusted to 68 knots (78 mph), and surface visibility was reduced to 2.2 miles (below).

A mid-latitude cyclone intensified as it moved northeastward across Nebraska, the eastern Dakotas and northern Minnesota (3-hourly surface analyses) during 25 December – 26 December 2016. GOES-13 (GOES-East) Water Vapor (6.5 µm) images (above) showed distinct banding within the warm conveyor belt, a well-defined dry slot, and a large comma head that formed from the cold conveyor belt. The storm produced blizzard conditions across much of the Northern Plains and Upper Midwest, with heavy snowfall (as much as 22.0inches in western North Dakota), freezing rain (ice accretion as thick as 0.5 inch in Minnesota and North Dakota) , sleet (up to 2.0 inches deep in Minnesota) and heavy rainfall; in Kansas there were also a few tornadoes (SPC storm reports).

A noteworthy characteristic of the storm was very strong winds — a closer view of GOES-13 Water Vapor imagery with hourly plots of surface wind gusts (in knots) is shown below.

GOES-13 Water Vapor (6.5 µm) images, with hourly surface wind barbs and wind gusts in knots [click to play animation]

Note the swath of wind gusts in the 50-60 knot range which progressed across central and northeastern Nebraska into northwestern Iowa and finally southwestern Minnesota during the 02 UTC to 12 UTC period on 26 December — this was pointed out in a tweet by Anthony Sagliani as a “sting jet” feature:

Beautiful example of a bent-back occlusion/sting jet tonight in the Northern Plains, complete with a "false" warm sector. pic.twitter.com/36ChcoGFqS

As observed in previous sting jet cases (03 Jan 2012 | 28 Oct 2013), the strongest winds occurred near the curved “scorpion tail” signature seen in the water vapor imagery (which marked the leading edge of the cold conveyor belt as it advanced into the rear edge of the dry slot of the cyclone circulation).

A closer view with Suomi NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images at 1952 UTC on 25 December (below) showed a detailed view of the banded cloud structures from Kansas into South Dakota, as well as small overshooting tops associated with thunderstorms in southeastern South Dakota and southwestern Minnesota. This storm produced the first Christmas Day thunderstorms on record in both Sioux Falls and Rapid City, South Dakota; thundersnow was also observed in Bismarck, North Dakota.